Principal CW Muon Facilities

produce continuous beams and are superior for
time-differential µSR
experiments requiring high time resolution.

Pulsed Muon Facilities

Others at the following labs produce pulsed beams
and are superior for long time range experiments
and those involving irradiation of the target with RF or laser power
during the muons' short lifetime (on average 2.2 µs).

The BOOM
(BOOster Muon) facility of the
KEK
laboratory in Japan and the associated
Meson Science Lab
have now been superceded by the
J-PARC
accelerator centre in Tokai.

Other Accelerator Labs with Muon Capabilities

The high-intensity µSR
facility at the Clinton P. Anderson Meson Physics Facility
(LAMPF)
was just beginning to find its optimal use
when the facility was shut down.
There was hope for utilizing this
world's brightest muon source for µSR
experiments if the proposed Pulsed Lepton Facility
had been built for the Proton Storage Ring, in which case
LAMPF would have become a pulsed muon facility.

There are also µSR facilities at the
JINR
lab in Dubna (Russia) but their future is uncertain.

In principle, any high-intensity hadron accelerator
of greater than about 400 MeV incident kinetic energy
should be capable of producing useful muon beams. A
list of the world's accelerators, organized into
various categories, is maintained at LANL.

The time structure of the beam should be
either CW or very sharply pulsed (pulse widths as
short as possible, but no greater than about 100 ns,
with at least 20 µs between pulses)
to produce the best results, but time-integral methods
can make use of any muon beams.

Editorial comment by Jess Brewer :

The main impediment to expanded use of µSR
has always been political: the high energy physics community
that used to have sole responsible for
the construction of large accelerators
is not always enthusiastic about sharing their resources
with the materials scientists who make up the bulk of
the µSR user community;
meanwhile, as the materials science community begins to
regard large accelerators as valuable resources,
it is predominantly for the sake of their
production of spallation neutrons for investigations
in k-space.
Both communities suffer when they ignore the opportunity
for cooperative alliance offered by µSR
and continue to see each other (and µSR) as adversaries.
There are a few hopeful signs of enlightened self-interest
in this decades-old struggle, but the tradition of
animosity between narrow interest groups is still the
worst enemy of cooperative scientific inquiry.